1. Field of the Invention
The present invention relates to a reciprocating compressor, and more particularly, to a reciprocating compressor capable of reducing a usage amount of an expensive magnet, enhancing an output of a driving motor, and simplifying components.
2. Description of the Conventional Art
Generally, a reciprocating compressor is a device for sucking refrigerant gas and compressing the refrigerant gas as a piston is linearly-reciprocated in a cylinder. The reciprocating compressor is largely divided into two by a driving mechanism. One is for converting a rotary motion of a motor into a linear reciprocation and then transmitting the converted linear reciprocation to a piston, and another is for directly transmitting a linear reciprocation of a motor to a piston.
FIG. 1 shows one example of a reciprocating compressor in which a linear reciprocation of a motor is directly transmitted to a piston. As shown, the reciprocating compressor comprises: a casing 10 to which a gas suction pipe 1 and a gas discharge pipe 2 are coupled; a front frame 20 and a middle frame 30 elastically supported in the casing 10 with a certain interval; a driving motor 40 mounted between the front frame 20 and the middle frame 30, for generating a driving force; a cylinder 50 inserted into the front frame 20; a piston 60 linearly-reciprocated in the cylinder 50 by receiving a driving force of the driving motor 40; a rear frame 70 covering the piston 60; a resonance spring 80 for inducing a resonance by elastically supporting the piston 60; and a valve assembly 90 for opening and closing a gas flow path so that gas can be sucked into the cylinder 50 and compressed as the piston 60 is linearly-reciprocated.
The driving motor 40 includes: an outer stator 41 mounted between the front frame 20 and the middle frame 30; an inner stator 42 inserted into the outer stator 41 with a certain interval thereby to be mounted at the front frame 20; a winding coil 43 coupled to the outer stator 41; and a mover 44 linear-movably inserted between the outer stator 41 and the inner stator 42.
The mover 44 is composed of a cylindrical holder 45, and a plurality of magnets 46 coupled to the holder 45. The holder 45 is connected to the piston 60.
The outer stator 41 is formed as a cylindrical shape having a certain length, and an opening groove 41a at which the winding coil 43 is positioned is formed at an inner circumferential surface of the outer stator 41. A pole portion 41b is formed at both sides of the opening groove 41a. 
The inner stator 42 is formed as a cylindrical shape having a certain length, and a sectional surface of one side thereof has a square shape.
The outer stator 41 and the inner stator 42 are formed as a plurality of lamination sheets having a certain shape are stacked.
As shown in FIG. 2, a length L1 of the magnet 46 in an axial direction is the sum of a length L2 of the opening groove 41a of the outer stator and a length L3 of one pole portion. Under a state that the magnet 46 is coupled to the holder 45, both ends of the magnet 46 are respectively positioned at the middle part of the pole portion 41b.
The valve assembly 90 is composed of: a discharge cover 91 coupled to the front frame 20, for covering one side of the cylinder 50; a discharge valve 92 positioned in the discharge cover 91, for opening/closing one side of the cylinder 50; a valve spring 93 positioned in the discharge cover 91, for elastically supporting the discharge valve 92; and a suction valve 94 coupled to an end portion of the piston 60, for opening and closing an inner flow path 61 penetratingly formed in the piston 60.
An unexplained reference numeral 21 denotes a coupling bolt, and 22 to denotes a nut.
An operation of the reciprocating compressor will be explained as follows.
First, when power is supplied to the driving motor 40, a current flows on the winding coil 43 of the driving motor 40. By the current, a flux is formed at the outer stator 41 and the inner stator 42. By an interaction between the generated flux and a flux formed by the magnet 46 of the mover 44, the mover 44 is linearly-reciprocated and thereby the piston 60 connected to the mover 44 is linearly-reciprocated in the cylinder 50.
As the piston 60 is linearly reciprocated in the cylinder 50, a pressure difference is generated in the cylinder 50. By the pressure difference inside the cylinder 50, the suction valve 94 and the discharge valve 92 constituting the valve assembly 90 open and close the gas flow path thereby to suck gas into the cylinder 50, compress the gas, and discharge the gas. While the above processes are repeated, sucked gas is continuously compressed.
In order to enhance a price competitiveness of a compressor, components and fabrication processes have to be simplified. Also, in order to minimize a consumption power, an output of a driving motor has to be maximized.
However, in the conventional reciprocating compressor, the magnets 46 are positioned at the air gap between the outer stator 41 and the inner stator 42 under a state of being mounted on the holder 45. According to this, the holder 45 for fixing the magnets 46 is required thus to have complicated components and to increase a fabrication cost of the holder 45. Also, since the holder 45 is used, the air gap between the outer stator 41 and the inner stator 42 becomes relatively large thereby to generate a motor loss.
Also, since both ends of the magnet 46 are respectively positioned at the middle part of the pole portion 41b of the outer stator, the length L1 of the magnet 46 becomes relatively long and thereby a usage amount of the magnets 46 mounted at the holder 45 is excessively increased. As the magnet 46 is very expensive, the entire fabrication cost is increased.